Coupled-clay is a bi-directional 3D collaborative interactive environment that supports the 3D modelling work between groups of users at remote locations. It consists of two network-connected workspaces, the Physical Interaction Space and the Virtual Interaction Space. The physical interaction space allows a user to directly manipulate a physical object whose shape and position are precisely tracked. This tracked 3D information is transferred to the virtual interaction space in real time. The virtual interaction space is made of an interactive multi-user stereoscopic 3D tabletop, or other 3D displays with adequate interaction device. The users at the virtual interaction space observe the virtual 3D object which corresponds to the physical object and manipulate its geometrical attributes (e.g., translation, rotation and scaling). Additionally, they can control the graphical attributes of the virtual object such as color and texture. Information about changes in geometrical and graphical attributes are sent back to the physical interaction space in real time and reflected to the object in the physical interaction space by a robotic arm and a top-mounted projector. Coupled-clay can be used to remotely collaborate on 3D modelling tasks between a skilled designer and novice learners.